Field of the Invention
Exemplary embodiments of the present invention relate to a microwave tomography system; and, more particularly, to a phase measurement device and method in a microwave tomography system.
Description of Related Art
A microwave tomography system emits a microwave signal onto a measurement target, measures the magnitude and phase value of a scattered microwave signal, and analyzes inverse scattering using the measured magnitude and phase value of the microwave signal. Through this operation, the microwave tomography system can calculate internal permittivity and conductivity of the measurement target. Thus, the microwave tomography system can perform nondestructive inspection for the inside of the measurement target. The phase value of the scattered microwave, measured through the microwave tomography system, must be an unwrapped phase value. However, when the measured phase value is a wrapped phase value, a result value obtained through the inverse scattering analysis may diverge or the precision of the analysis may decrease. For example, when the unwrapped phase value of the scattered microwave signal is 400 degrees, the phase value may be expressed as a wrapped phase value of 40 degrees (400 degrees-360 degrees). In this case, when the inverse scattering analysis is performed through the wrapped phase value of 40 degrees, the result value may diverge or become incorrect.
The microwave tomography system may acquire phase-unwrapped data through the following method. The microwave tomography system emits microwave signals onto a measurement target at various frequencies from a low frequency to a high frequency at a predetermined interval, receives scattered microwave signals, compares phase values measured at the low frequency and the high frequency, respectively, and determines whether the measured phase values are unwrapped values.
According to the method for acquiring unwrapped data in the microwave tomography system, the phase value at the initial low frequency must not be unwrapped. Furthermore, in order to find a phase value at the high frequency, the microwave tomography system must measure phase values while sequentially changing the frequency from the phase value at the low frequency. Thus, the microwave tomography system must have a function of transmitting/receiving wideband microwave signals.
The microwave tomography system must change the frequency from the low frequency to the high frequency. Thus, the measurement time and the cost required for constructing the system are inevitably increased.